High Particle Number Research Articles

Collisional growth in a particle-based cloud microphysical model: insights from column model simulations using LCM1D (v1.0)

Abstract. Lagrangian cloud models (LCMs) are considered the future of cloud microphysical modelling. Compared to bulk models, however, LCMs are computationally expensive due to the typically high number of simulation particles (SIPs) necessary to represent microphysical processes such as collisional growth of hydrometeors successfully. In this study, the representation of collisional growth is explored in one-dimensional column simulations, allowing for the explicit consideration of sedimentation, complementing the authors' previous study on zero-dimensional collection in a single grid box. Two variants of the Lagrangian probabilistic all-or-nothing (AON) collection algorithm are tested that mainly differ in the assumed spatial distribution of the droplet ensemble: the first variant assumes the droplet ensemble to be well-mixed in a predefined three-dimensional grid box (WM3D), while the second variant considers the (sub-grid) vertical position of the SIPs, reducing the well-mixed assumption to a two-dimensional, horizontal plane (WM2D). Since the number of calculations in AON depends quadratically on the number of SIPs, an established approach is tested that reduces the number of calculations to a linear dependence (so-called linear sampling). All variants are compared to established Eulerian bin model solutions. Generally, all methods approach the same solutions and agree well if the methods are applied with sufficiently high resolution (foremost is the number of SIPs, and to a lesser extent time step and vertical grid spacing). Converging results were found for fairly large time steps, larger than those typically used in the numerical solution of diffusional growth. The dependence on the vertical grid spacing can be reduced if AON-WM2D is applied. The study also shows that AON-WM3D simulations with linear sampling, a common speed-up measure, converge only slightly slower compared to simulations with a quadratic SIP sampling. Hence, AON with linear sampling is the preferred choice when computation time is a limiting factor. Most importantly, the study highlights that results generally require a smaller number of SIPs per grid box for convergence than previous one-dimensional box simulations indicated. The reason is the ability of sedimenting SIPs to interact with a larger ensemble of particles when they are not restricted to a single grid box. Since sedimentation is considered in most commonly applied three-dimensional models, the results indicate smaller computational requirements for successful simulations, encouraging a wider use of LCMs in the future.

Regional Inhaled Deposited Dose of Indoor Combustion-Generated Aerosols in Jordanian Urban Homes

Indoor combustion processes associated with cooking, heating, and smoking are a major source of aerosols in Jordanian dwellings. To evaluate human exposure to combustion-generated aerosols in Jordanian indoor environments, regional inhaled deposited dose rates of indoor aerosols (10 nm to 25 µm) were determined for different scenarios for adult occupants. The inhaled deposited dose rate provides an estimate of the number or mass of inhaled aerosol that deposits in each region of the respiratory system per unit time. In general, sub-micron particle number (PN1) dose rates ranged from 109 to 1012 particles/h, fine particle mass (PM2.5) dose rates ranged from 3 to 216 µg/h, and coarse particle mass (PM10) dose rates ranged from 30 to 1600 µg/h. Dose rates were found to be dependent on the type and intensity of indoor combustion processes documented in the home. Dose rates were highest during cooking activities using a natural gas stove, heating via natural gas and kerosene, and smoking (shisha/tobacco). The relative fraction of the total dose rate received in the head airways, tracheobronchial, and alveolar regions varied among the documented indoor combustion (and non-combustion) activities. The significant fraction of sub-100 nm particles produced during the indoor combustion processes resulted in high particle number dose rates for the alveolar region. Suggested approaches for reducing indoor aerosol dose rates in Jordanian dwellings include a reduction in the prevalence of indoor combustion sources, use of extraction hoods to remove combustion products, and improved ventilation/filtration in residential buildings.

Simple method to extend the range of ECO-BB for waters with high backscattering coefficient.

The ECO-BB (Sea Bird Scientific) is a popular instrument used by water optics researchers to measure the backscattering coefficient of waters in the visible to near-infrared wavelengths. The ECO-BB is calibrated by default for oceanic waters where the backscattering coefficient is typically low. In inland and coastal waters however, there is a tendency for the ECO-BB to reach saturation due to the high number of suspended particles. In the paper, a simple method is presented to extend the range of the ECO-BB instrument in such waters using a nephelometric turbidimeter. The method was first tested on powdered calcium carbonate in pure freshwater, followed by collected water samples from the Singapore Straits and the Lupar River in Sarawak. All three tests confirm the correlation between the ECO-BB and turbidimeter and show that the turbidimeter is a good proxy for backscattering coefficient measurements in turbid waters.

Characteristics of instantaneous particle number (PN) emissions from hybrid electric vehicles under the real-world driving conditions

The control strategy of hybrid vehicles is mainly optimized for better fuel efficiency and hybrid electric vehicles were reported to have higher particle emissions than conventional vehicles. To assess the high instantaneous particle number (PN) emission characteristics, four hybrid electric vehicles with different technical parameters were tested under real-world driving conditions. The high instantaneous PN emission was clustered as high emission sets (HES) and HES were evaluated with the vehicle driving conditions and engine operating conditions. The results revealed that 20% of the accumulated particles are emitted within 2% of the driving time and 80% of the accumulated particles are emitted within 20% of the driving time. Most of the HES are observed at the speed lower than 60 km/h (urban speed limit), with relatively higher engine speed. HES have higher mean positive acceleration values than their RDE counterparts. But the largest acceleration doesn’t represent high particle emission, because, with the electric motor, acceleration is decoupled with the engine variation. The HES could be observed at rich/lean fuel conditions, high/low state of charge, and before/after the engine is fully warmed-up depending on the vehicle’s technical characteristics. Regeneration could increase the PN emission by a factor of five. Fuel-efficiency centered strategy should be combined with the pollutant-control centered strategy to achieve cleaner hybrid technology. These results could also be useful in future policies and PN emission models.

Methods Matter: Methods for Sampling Microplastic and Other Anthropogenic Particles and Their Implications for Monitoring and Ecological Risk Assessment

To inform mitigation strategies and understand how microplastics affect wildlife, research is focused on understanding the sources, pathways, and occurrence of microplastics in the environment and in wildlife. Microplastics research entails counting and characterizing microplastics in nature, which is a labor-intensive process, particularly given the range of particle sizes and morphologies present within this diverse class of contaminants. Thus, it is crucial to determine appropriate sampling methods that best capture the types and quantities of microplastics relevant to inform the questions and objectives at hand. It is also critical to follow protocols with strict quality assurance and quality control (QA/QC) measures so that results reflect accurate estimates of microplastic contamination. Here, we assess different sampling procedures and QA/QC strategies to inform best practices for future environmental monitoring and assessments of exposure. We compare microplastic abundance and characteristics in surface-water samples collected using different methods (i.e., manta and bulk water) at the same sites, as well as duplicate samples for each method taken at the same site and approximate time. Samples were collected from 9 sampling sites within San Francisco Bay, California, USA, using 3 different sampling methods: 1) manta trawl (manta), 2) 1-L grab (grab), and 3) 10-L bulk water filtered in situ (pump). Bulk water sampling methods (both grab and pump) captured more microplastics within the smaller size range (<335 µm), most of which were fibers. Manta samples captured a greater diversity of morphologies but underestimated smaller-sized particles. Inspection of pump samples revealed high numbers of particles from procedural contamination, stressing the need for robust QA/QC, including sampling and analyzing laboratory blanks, field blanks, and duplicates. Choosing the appropriate sampling method, combined with rigorous, standardized QA/QC practices, is essential for the future of microplastics research in marine and freshwater ecosystems. Integr Environ Assess Manag 2021;17:282-291. © 2020 SETAC.

Effect of extrusion ratio and temperature on microstructures and tensile properties of extruded Mg-Gd-Y-Mn-Sc alloy

This study analyzed the effect of extrusion parameters on the microstructural evolution and tensile properties of a Mg-8.0Gd-4.0Y-1.0Mn-0.4Sc (wt.%) alloy. The variation in the dynamic recrystallization (DRX) and dynamic precipitation behavior of the alloy under different extrusion parameters were investigated in detail, and the DRX behavior during hot extrusion and strengthening mechanism were revealed. The primary DRX mechanisms are discontinuous dynamic recrystallization (DDRX), continuous dynamic recrystallization (CDRX). The as-extruded alloy with larger extrusion ratio exhibits smaller dynamic recrystallized (DRXed) grains and a high number of fine precipitated particles. With increasing the extrusion temperature, both the average size and volume fraction of DRXed grain increase, but the fine particle fraction decreases. The alloy extruded at 400 °C and ratio of 20:1 shows the superior strength with tensile yield strength of 352 MPa and ultimate tensile strength of 425 MPa, and the alloy extruded at 450 °C and ratio of 10:1 shows higher elongation to failure of 12%. The enhanced strength is mainly attributed to the combined action of strong basal texture, refined DRXed grains and dense distribution of fine particles, on the other hand, the higher fraction of DRXed grains and lower amount of precipitate particles are beneficial to increase the ductility of the alloy.

Direct numerical simulations of nanoparticle formation in premixed and non-premixed flame–vortex interactions

Direct numerical simulations (DNSs) of nanoparticle formation in reactive flows are challenging, and only greatly simplified DNS test-cases are possible, which help clarify the turbulence–particle–dynamics interaction and guide the necessary modeling efforts. As a basis for such studies, a new DNS database is introduced, which resolves the smallest relevant scales of the nanoparticle concentration field to obtain insights into the statistics of nanoparticle formation in reactive flows. Formation and evolution of iron oxide nanoparticles in premixed and non-premixed flames wrapped-up by a vortex have been investigated using the sectional model and direct chemistry. The DNSs capture the “engulfing” and local dilution of the particle fields. Different zones of high particle number concentration have been found in every flame, and it was shown that the thickness of these zones decreases with increasing Schmidt number, which confirms that in simulations of nanoparticle-forming turbulent reacting flows, the grid resolution has to be very fine to resolve the characteristic scale for high sections. The contributions to the change in particle concentration due to diffusion, coagulation, and nucleation have been analyzed in detail, and dominant contributions across the particle number concentration layers and across the flames have been identified. This analysis has also been carried out in terms of flat, concave, and convex iso-surface geometries, induced by the flame–vortex interaction and characterized by the curvature of the particle number concentration fields and also by the flame curvature. The results demonstrate that the flame curvature effects cannot be ignored in modeling strategies. The probability density functions for the particle number concentrations have been analyzed and quantified in terms of Shannon information entropy, which illustrates the effect of fast diffusion (and entropy production) of the smaller particles and slow diffusion (and entropy production) of the largest particles with high Schmidt numbers. In addition, the unclosed filtered or averaged agglomeration term was evaluated as a basis for future modeling efforts, showing that agglomeration rates will be underestimated by orders of magnitude unless suitable models are developed.

Oxidative damage and decreased aerobic energy production due to ingestion of polyethylene microplastics by Chironomus riparius (Diptera) larvae

Riverine sediments are major sinks of microplastics from inland anthropogenic activities, imposing a threat to freshwater benthic invertebrates. This study investigated the ingestion of three size-classes (SC) of irregularly shaped polyethylene microplastics (PE-MPs; SC I: 32−63 μm; II: 63−250 μm; III: 125−500 μm) after 48 h by dipteran larvae (detritivore/collector) Chironomus riparius, and the consequent effects on neurotransmission, energy allocation and oxidative stress. The tested PE-MPs concentrations (1.25; 5; 20 g kg−1) were within the range of concentrations reported in riverbanks from highly urbanised areas (1 - 9 g kg−1), except for 20 g kg−1 representing the worst-case scenario. After exposure to SC I, larvae presented high amounts (up to ∼2400 particles/organism) of PE-MPs in their guts, with an average size-range of 30−60 μm. In the SC II and III, larvae presented PE-MPs of higher diameter (up to 125 μm) and a visible gut obstruction. The high number of particles in the larval gut (SC I) and/or difficulties for their egestion (SC I, II and III) induced oxidative damage and reduced aerobic energy production. In addition, larvae exposed to SC II and III revealed depletion in their total lipid reserves as a consequence of lacking nutrients, and the ones exposed to SC III presented a decrease in their detoxification capacity.These results highlight that freshwater detritivores with low selective feeding behaviour (e.g., chironomids) are more prone to ingest microplastics, with potentially adverse effects on cellular metabolism, redox status and antioxidant-detoxification defences. These harmful effects at lower levels of the biological organisation may ultimately affect organisms’ physiology and fitness.

Impact of Microwave Plasma Torch on the Yeast Candida glabrata

Recently, various cold plasma sources have been tested for their bactericidal and fungicidal effects with respect to their application in medicine and agriculture. The purpose of this work is to study the effects of a 2.45 GHz microwave generated plasma torch on a model yeast example Candida glabrata. The microwave plasma was generated by a surfatron resonator, and pure argon at a constant flow rate of 5 Slm was used as a working gas. Thanks to a high number of active particles generated in low-temperature plasma, this type of plasma has become highly popular, especially thanks to its bactericidal effects. However, its antimycotic effects and mechanisms of fungal inactivation are still not fully understood. Therefore, this study focuses on the antifungal effects of the microwave discharge on Candida glabrata. The main focus is on the measurement and evaluation of changes in inactivation effects caused by varying initial concentration of Candida glabrata cells, applied microwave power and exposure time. The discharge was applied on freshly inoculated colonies of Candida glabrata spread on the agar plates and its inhibitory effects were observed in the form of inhibition zones formed after the subsequent cultivation.

Effects of continental emissions on cloud condensation nuclei (CCN) activity in the northern South China Sea during summertime 2018

Abstract. Aerosol particles in marine atmosphere have been shown to significantly affect cloud formation, atmospheric optical properties, and climate change. However, high temporally and spatially resolved atmospheric measurements over the sea are currently sparse, limiting our understanding of aerosol properties in marine atmosphere. In this study, a ship-based cruise campaign was conducted over the northern South China Sea (SCS) region during summertime 2018. The chemical composition of non-refractory PM1 (NR-PM1), the particle number size distribution (PNSD), and size-resolved cloud condensation nuclei (CCN) activity were measured by a time-of-flight aerosol chemical speciation monitor (ToF-ACSM) and the combination of a cloud condensation nuclei counter (CCNc) and a scanning mobility particle sizer (SMPS). Overall, aerosol particles exhibited a unimodal distribution centering at 60–80 nm and the chemical composition of the NR-PM1 was dominated by sulfate (∼ 46 %), which likely originated from anthropogenic emissions rather than dimethyl sulfide (DMS) oxidation. Two polluted episodes (P1 and P2) were observed, and both were characterized by high particle number concentrations (NCN) which originated from local emissions and from emissions in inland China via long-range transport. The concentrations of trace gases (i.e., O3, CO, NOx) and particles (NCN and NCCN at ss = 0.34 %) were elevated during P2 at the end of the campaign and decreased with offshore distance, further suggesting important impacts of anthropogenic emissions from the inland Pearl River Delta (PRD) region. Two relatively clean periods (C1 and C2) prior to and after tropical storm Bebinca were classified and the air was affected by air masses from the southwest and from the Indo-Chinese Peninsula, respectively. Chemical composition measurements showed an increase in organic mass fraction during P2 compared to C2; however, no obviously different κ values were obtained from the CCNc measurements, implying that the air masses carried pollutants from local sources during long-range transport. We report an average value of about 0.4 for the aerosol hygroscopicity parameter κ, which falls within the literature values (i.e., 0.2–1.0) for urban and remote marine atmosphere. In addition, our results showed that the CCN fraction (NCCN∕NCN, tot) and the κ values had no clear correlation either with the offshore distance or with concentrations of the particles. Our study highlights dynamical variations in particle properties and the impact of long-range transport from continental China and the Indo-Chinese Peninsula on the northern SCS region during summertime.

Nutritional Features and Bread-Making Performance of Wholewheat: Does the Milling System Matter?

Despite the interest in stone-milling, there is no information on the potential advantages of using the resultant wholegrain flour (WF) in bread-making. Consequently, nutritional and technological properties of WFs obtained by both stone- (SWF) and roller-milling (RWF) were assessed on four wheat samples, differing in grain hardness and pigment richness. Regardless of the type of wheat, stone-milling led to WFs with a high number of particles ranging in size from 315 to 710 μm), whereas RWFs showed a bimodal distribution with large (>1000 μm) and fine (<250 μm) particles. On average, the milling system did not affect the proximate composition and the bioactive features of WFs. The gluten aggregation kinetics resulted in similar trends for all SWFs, with indices higher than for RWFs. The effect of milling on dough properties (i.e., mixing and leavening) was sample dependent. Overall, SWFs produced more gas, resulting in bread with higher specific volume. Bread crumb from SWF had higher lutein content in the wheat cv rich in xanthophylls, while bread from RWF of the blue-grained cv had a moderate but significantly higher content in esterified phenolic acids and total anthocyanins. In conclusion, there was no relevant advantage in using stone- as opposed to roller-milling (and vice versa).

A review of respiratory protection measures recommended in Europe for dental procedures during the COVID-19 pandemic

The main mode of transmission of the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) virus is via respiratory droplets and aerosols [1]. During the coronavirus disease 2019 (COVID-19) pandemic period, the World Health Organization (WHO) recommends wearing respiratory protection when undertaking aerosol-generating procedures (AGPs) to reduce the risk of cross-infection between patients and healthcare workers (HCWs) and vice versa [2]. Patients who test positive for this virus are known to carry high numbers of virus particles in their saliva and on their tongue [3].

Vibrations as a cause of texture defects during the acid-induced coagulation of milk – Fluid dynamic effects and their impact on physical properties of stirred yogurt

Abstract Vibrations during yogurt fermentation have been reported to disturb the gelation by inducing large, visible particles. Such vibrations are generated by the machinery used for the industrial manufacture and can cause structural excitation of the fermentation tanks. To study the effect of vibrations on yogurt structure, an experimental setup was constructed consisting of a cylindrical tank (height: 600 mm). The bottom of the tank was excited by a shaker, resulting in a vertical vibration propagation. Skim milk was vibrated during fermentation at 30 Hz and different amplitudes. Vibrated gels showed syneresis up to ∼5%. Samples were taken at different height positions of the fermenter, processed into stirred yogurt, and analyzed. The number of large particles was primarily related to the set vibration amplitude, however, particle formation was more pronounced in the lower and upper area. Yogurts with a high particle number exhibited a reduced water-holding capacity and apparent viscosity. Moreover, the fluid dynamic effects of vibrations were investigated by particle image velocimetry. Vibrations led to uniform to-and-fro motions, whereas chaotic flow was observed at the surface. Finally, the impact of vibrations on the gelation mechanism is discussed.

Computationally inexpensive simulation of agglomeration in spray drying while preserving structure related information using CFD

Controlled agglomeration during spray drying offers several advantages for both powder manufacturers and consumers, and thus it is commonly implemented by industry. The implementation, however is largely based on experience, given the scarcity of comprehensive prediction tools. A resource-efficient approach to numerically treat agglomerates and yet provide an indication of their structures is desired to perform realistic simulations without the need for high-performance computing. In this work, a new numerical model for the treatment of coalescence and agglomeration was implemented and evaluated at two distinct scales with significantly different particle number densities within a Eulerian-Lagrangian CFD framework. The model could accurately predict the trends in the final particle size distributions and distinguish realistic agglomerate structures occurring under different conditions. Challenges were encountered as a result of how the underlying collision detection routine handles high particle number density. Several strategies are proposed to overcome these challenges. This work constitutes significant progress towards achieving an efficient prediction tool to estimate final powder properties and will prove useful in performing large-scale simulations to design and control agglomeration.

When to lower triglycerides?

Substantial risk of ASCVD events persists despite intensive statin therapy and other agents to lower LDL-C. The optimal way to address other elements of dyslipidemia, such as triglyceride-rich particles (TRL) and when to treat has remained unclear. Several lines of evidence indicate that TRL are associated with atherogenesis, partly because of associated factors, such as cholesterol-enriched remnant particles, high LDL particle number, high apo-B, high apo-CIII, and others. High triglyceride is increasingly prevalent because of worsening of lifestyle factors, obesity, and diabetes. Trials with fibrates, and niacin to reduce residual dyslipidemia have not provided evidence of benefits after statin therapy, thus far. A recent trial with an omega 3 fatty acid (OM3FA), icosapent-ethyl (IPE), provided evidence for a 25% reduction in ASCVD events in statin-treated high-risk population. These results were unexplained by triglyceride reduction alone, and are likely related to unique biologic effects of IPE on atherosclerosis. Finally, in patients with very high triglycerides, lifestyle measures and several triglyceride-lowering agents are indicated, often in combination, to prevent episodes of pancreatitis. A novel Apo C-III inhibitor may provide additional benefit in such patients. There is evidence for the benefits of IPE in preventing ASCVD events. A novel fibrate is in clinical trials.

Analysis of the relationship between particle number and fuel cutoff in a single-cylinder gasoline direct injection engine

This study investigates the effects of fuel cutoff on particle number in a single-cylinder wall-guided gasoline direct injection engine. Various durations of fuel cutoff and change in load and engine stop were tested, and the in-cylinder pressure, particle number, and NO x emissions were measured. The change in in-cylinder temperature during combustion stop was calculated using the in-cylinder pressure and the ideal gas law. Experimental results showed that as the fuel cutoff duration increased, the particle number increased significantly when combustion resumed. For the injection timing before top dead center 330°, the particle number, which was 600 × 103 #/cm3 under the continuous combustion condition, increased to 6700 × 103 #/cm3 after 30 s of fuel cutoff. Both the fuel cutoff and engine stop showed enormous amount of particle number when combustion restarted. A major factor that increased particle number was the temperature reduction of piston during the combustion stop. The peak in-cylinder temperature decreased by 38 K during 30 s of motoring, which was induced by the temperature drop of the piston. Therefore, in terms of particulate emissions, it is more advantageous to lower the engine load than to stop combustion: the piston surface remains hot during load reduction. In addition, it is recommended to change the engine load slowly to reduce the particle number emissions. In this study, the rapid load change from indicated mean effective pressure of 0.25 to 0.55 MPa showed 7% higher particle number emissions than the gentle load change. On the contrary, NO x was reduced because none was generated during combustion stop. However, the fuel cutoff would increase NO x in gasoline vehicles because the oxygen in the unburned air would significantly reduce the conversion efficiency of a three-way catalytic converter. It is especially worth investigating the reason for the increase in emissions because it is easy to think that all kinds of emissions will be reduced if fuel is not burned.

The first, holistic immunological model of COVID-19: Implications for prevention, diagnosis, and public health measures.

The natural history of COVID‐19 caused by SARS‐CoV‐2 is extremely variable, ranging from asymptomatic or mild infection, mainly in children, to multi‐organ failure, eventually fatal, mainly in the eldest. We propose here the first model explaining how the outcome of first, crucial 10‐15 days after infection, depends on the balance between the cumulative dose of viral exposure and the efficacy of the local innate immune response (natural IgA and IgM antibodies, mannose‐binding lectin). If SARS‐CoV‐2 runs the blockade of this innate immunity and spreads from the upper airways to the alveoli in the early phases of the infections, it can replicate with no local resistance, causing pneumonia and releasing high amounts of antigens. The delayed and strong adaptive immune response (high‐affinity IgM and IgG antibodies) that follows, causes severe inflammation and triggers mediator cascades (complement, coagulation, and cytokine storm), leading to complications often requiring intensive therapy and being, in some patients, fatal. Low‐moderate physical activity can still be recommended. However, extreme physical activity and oral breathing with hyperventilation during the incubation days and early stages of COVID‐19 facilitates re‐inhalation and early direct penetration of high numbers of own virus particles in the lower airways and the alveoli, without impacting on the airway’s mucosae covered by neutralizing antibodies ("viral auto‐inhalation" phenomenon). This allows the virus to bypass the efficient immune barrier of the upper airway mucosa in already infected, young, and otherwise healthy athletes. In conclusion, whether the virus or the adaptive immune response reaches the lungs first is a crucial factor deciding the fate of the patient. This “quantitative and time‐/sequence‐dependent” model has several implications for prevention, diagnosis, and therapy of COVID‐19 at all ages.

Experimental Exposure of Lumbricus terrestris to Microplastics

The effects of microplastic exposure in aquatic organisms have been widely reported. Nonetheless, there is limited evidence of the effects of exposure in soil systems. Thus, the objective of this study was to evaluate the effects of microplastic exposure using as a bioindicator the species Lumbricus terrestris, exposed to different concentrations of microplastic (2.5%; 5%, and 7% w/w). Avoidance bioassays were carried out for 48 h in soil with and without microplastic; the gastrointestinal tract—crop/gizzard, foregut, and midgut—was dissected and acetylcholinesterase (AChE) was used as a biomarker of neurotoxicity stress. In parallel, bioassays of microplastic ingestion were carried out, and after 48 h of initiating the ingestion assay, using a stereo and fluorescence microscope, the microplastic distribution was observed in the different earthworm segments. The results obtained in the avoidance assay indicated a lack of preference for either soil type; however, upon moving, the earthworms lost surface mucus, resulting in burns and lesions on their bodies, which were reflected in the increase in AChE enzyme levels, which was not directly related to microplastic ingestion, but rather likely acts as an external physical stress agent. The results of the ingestion bioassay showed that microplastic was present in all the earthworm segments, with a higher number of particles in the hindgut. The Lumbricus terrestris did not distinguish microplastics from soil particles, and given the high exposure concentrations, microplastics produced physical lesions on the mucus membranes of earthworms. Lumbricus terrestris showed to be a suitable bioindicator for testing the exposure to microplastic contamination in soil.

Assessment of 10-nm Particle Number (PN) Portable Emissions Measurement Systems (PEMS) for Future Regulations.

The particle number (PN) emissions of vehicles equipped with particulate filters are low. However, there are technologies that can have high PN levels, especially below the currently lower regulated particle size of 23 nm. Sub-23-nm particles are also considered at least as dangerous as the larger ultrafine particles. For this reason, the European Union (EU) is planning to regulate particles down to 10 nm. In this study we compared prototype portable emission measurement systems (PEMS) and reference laboratory systems measuring from 10 nm. The tests included cycles and constant speeds, using vehicles fuelled with diesel, gasoline or liquefied petroleum gas (LPG). The results showed that the PEMS were within ±40% of the reference systems connected to the tailpipe and the dilution tunnel. Based on the positive findings and the detection efficiencies of the prototype instruments, a proposal for the technical specifications for the future regulation was drafted.

Particle Number Emissions of a Diesel Vehicle during and between Regeneration Events

All modern diesel vehicles in Europe are equipped with diesel particulate filters (DPFs) and their particle number (PN) emissions at the tailpipe are close to ambient air levels. After the Dieselgate scandal for high NOx emissions of diesel vehicles on the road, the high PN emissions during regeneration events are on the focus. The PN emissions of a diesel vehicle on the road and in the laboratory with or without regeneration events were measured using systems with evaporation tubes and catalytic strippers and counters with lower sizes of 23, 10 and 4 nm. The tests showed significant PN levels only during engine cold starts with a big fraction of sub-23 nm particles during the first minute. After the first seconds the sub-23 nm fraction was negligible. Urea injection at the selective catalytic reduction (SCR) for NOx system did not affect the PN levels and the sub-23 nm fraction. The emissions during regeneration events were higher than the PN limit, but rapidly decreased 2-3 orders of magnitude below the limit after the regeneration. Artificially high sub-10 nm levels were seen during the regeneration (volatile artifact) at the system with the evaporation tube. The regenerations were forced every 100–350 km and the overall emissions including the regeneration events were two to four times lower than the current laboratory PN limit. The results of this study confirmed the efficiency of DPFs under laboratory and on-road driving conditions.